Two-stroke internal combustion engine



Aug. 16, 1938. w. GRAB 2,127,114

' TWO-STROKE INTERNAL COMBUSTION ENGINE Filed April 19, 1937 2 Sheets-Sheet 1 Fig.7

' MYbe/m amb Aug. 16, 1938. w; GRAB 1 TWO-STROKE INTERNAL COMBUSTION. ENGINE Filed April 19, 1957 2 Sheets-Sheet 2 F I Fig.2

Jnrenlor:

MY/IE M GRAB Patented' Aug. 16, 1938 UNITED STATES-PATENT ow -let I "2.121.114 l I wmteim Grab, 46mm; in men, Germany Application'Apl-il is. 1m.-

' In Germany? I ZOlnlms. (Cl. 128-59) The object o! the invention is a two-stroke combustion engine with working cylinders which are alternately charged by a feed pump, in such a manner that the combustible charge supplleil .5 'to the working cylinders by the feed pump. Piston of helical direction from the top downwards, so

as to secure a perfect scavenging'of' the working 15 cylinders. By means of this structure, in view of the known constructions, a larger output per volume strokewill be obtained, so that for equal output, smaller dimensions and a reduced weight of the machine, maybe secured. 20 In the drawings a two-'stroke-engineis trated with two working cylinders, given by way of exampleand in accordance with the invention, the drawings comprising five figures.

Fig. 1 is a longitudinal section of the engine 25 P p? i Fig. 2 is a slde'elevatiomoi the feed pump in longitudinal section;

. mus- I through the two working cylinders and the feed Fig.3 illustrates the inlet port for the fresh gas mixture as seen from below; p

Fig. 4 is a section through theinlet port for the mirture on line A'BC oi Fig. 1;.

Fig. 5-isa section through the head of a working cylinder on line 13-1 of Fig. 1.'

In both working cylinders]. and 2, the'two 5 working pistons land 4, which are displaced 180, act on thecrank-shait I. The charge is introduced'fin the working cylinders each' time from the top into the cylinder head at 8 and I, and at this inlet, the entering mixture is caused to new along a helical sloping face starting from the top at the inlet-port and directeddownwards. As m'ay be seen in Fig. 3,- it may be observed that,

on the one hand, the charge is more readily intro-' duced into the working cylinder, while, on the other hand,- a progressive helical movement is -imparted to the mixture, so that thereby a rapid and perfect scavenging issecured, by the fact.

that the remaining spent gases from the last 50 working stroke will be caught by this turbulent movement to be expelled downwards, through the exhaust slits 8 and 9 provided in the working cylinders at the end of the stroke.

55 arranged the feed pump I II, the piston I I oi which Between the two working cylinders I and I is.

is actuated by the crank II. -In the form or embodiment illustrated in the.drawings,'the proportions are so selected that thecrank-shaft I.2, driven by the pair of gears II, II, rotates at twice the speed of the working crank-shaft 5, that its 5 stroke, however, is only one half of the stroke of the working pistons 4 and 4, that the piston diameter is twice the diameter of the workingp stons, so that, in this way, the feed pump supplying alternately the working cylinders delivers 10 at eachtime to a working cylinder a charge corresponding to the working volume, the same pressure being' provfdedin .the feed pump and the I working cylinder.

The distribution oi! the feed pump is controlled by the sleeve valve I, which is driven by the working crank-shaft l, by means of the forked connecting rod It. At I1 is connected the tubular conduit-starting from the carburetter and irom where the mixtureis sucked through the inlet port It oi the leeve valve into the charging room above the p ton II of the feed pump II. The gas mixtin'e penetrates alternately through the outlets is, in the inlet channel 20 of tne cylinder I and the inlet channel 2| oi the cylinder 2, both inlet channels conducting through the P rts I and "I.

The speeds of the working piston and-oi thesupply piston are the same, as the reciprocating movementoi the supply-piston isv as a whole equal 39 to the single stroke of the working piston. (For each stroke 01' the working piston, the supply- I piston operates a suction -stroke and a compres-' sion stroke. 'I'he'sleeve valve has half the stroke of the working piston and half the speed of the supply piston. The adjustment of the feed pump with respect to the working cylinders is such that. when the working cylinder pistons have opened. the exhaust slit for half the height during the downward movement, the supply of fresh gas mix- 40 fture by the i'eedpump is started in the working cylinder, as itisillustrated-in Fig; 1. The working piston, in its iurther-downward movement, completely frees the exhaust slitsuntil the stroke end and starts closing the same again slowly when its upward movement begins. As soon as the exhaust (ports are closed, the teed pump, in accordance with the selected dimensions cited by way of example, has pressed in the-cylinders 3/4 of the stroke volume of the saidcylinders, which corresponds, with the working cylinder volume irom the upper edge of the exhaust ports to the "start of thestroke from above. -The remainingstroke of 25% of the feed pump piston corre- Y sponds to the volume content of the part of the 5 I backward stroke made by the working piston from the starting end of the stroke from below. During the last fourth part of the movement of the supply piston, said feed pump will act as .a compressor, which supplies to the working cylinder,

under pressure, a gas volume corresponding to the height of the exhaust ports. This auxiliary charge prevents the loss of. volume in the working cylinders, which may be observed in known constructions of combustion motors having exhaust ports in the working cylinders, said loss corresponding to the height of the exhaust ports.

I claim:

1. In a two-stroke internal combustion engine comprising two working cylinders, working pistons therein, piston rods and a common crankshaft, an inlet port in each working cylinder close to the cylinder head, exhaust ports in the cylinder walls, a pump cylinder located between and in alinement with the working cylinders, a pump piston therein, an auxiliary crank-shaft connected to said pump piston, a two to one 'ratio driving gear between bothcrank-shafts, an

inlet port in the pump cylinder, oppositely arranged outlet ports in the pump cylinder forming direct communications with the inlet ports of the working cylinders'respectively, a sleeve-valve located between the pump cylinder and its piston, and an eccentric driving connection between the common crank-shaft and the sleeve-valve for controlling the supply of gas mixture to the working cylinders through said outlet and inlet ports;

2. In a two-stroke internal combustion engine comprising two working cylinders, working pistons therein, piston rods and a common crankshaft, an inlet port in each working cylinder close to the cylinder head, an inner helical slope extending tangentially from the inlet port inside the working cylinder, exhaust ports in the cylinder walls, a pump cylinder located between and in alinement with the working cylinders, a pump piston therein, an auxiliary crank-shaft connected to said pump piston, a two to one ratio driving gear between both crank-shafts, an inlet port in the pump cylinder, oppositely arranged outlet ports in the pump cylinder forming direct communications with the inlet ports of the working cylinders respectively, a sleeve-valve located between the pump cylinder and its piston, and an eccentric'driving connection between the common crank-shaft and the sleeve-valve for controlling the supply of gas mixture to the working cylinders through said outlet and inlet ports, the arrangement being such that the mixture is supplied to the working cylinders without compression during the main part of the charging stroke of the pump piston, a final supply being made under pressure during the remaining part of said charging stroke which corresponds to that part of the return stroke of the working piston necessary for closing the exhaust ports.

WILHELM GRAB. 

